22 



NATURE 



[November 5, 1891 



the years 1858 and 1878, and thirty quarto volumes containing 

 the measures of many of them. The Annals of the Neiu Y>rk 

 Academy of Sciences, vol. vi., June 1891, contains a catalogue of 

 these negatives. There are 139 negatives of the sun taken 

 between i860 and 1874, each of which has the time of exposure 

 marked upon it. Several negatives were taken of the eclipses 

 of i860, 1865, and 1869. The solar spectrum is the subject of 

 160 negatives and 14 positives. The list of lunar negatives 

 numbers 408, 40 of which are c <vered for protection. Mars 

 was photographed in 1877, and the transit of Mercury in the 

 following year. It is hoped soon to issue reductions of the 

 measures of the numerous negatives of stars and clusters. 



THE INSTITUTION OF MECHANICAL 

 ENGINEERS. 

 A GENERAL meeting of the Institution of Mechanical 

 ■^ Engineers was held on Wednesday and Thursday even- 

 ings of last week, the 28th and 29th ultimo. The meeting took 

 place at the Institution of Civil Engineers, Great George Street, 

 the theatre having been lent by the Council of the latter Society 

 for the purpose. The President, Mr. Joseph Tomlinson, occu- 

 pied the chair, and there were two papers on the agenda. The 

 first of these, taken at the Wednesday's sitting, was " On some 

 Details in the Construction of Modern Lancashire Boilers," by 

 Mr. Samuel Boswell, of Manchester. The evening of Thursday 

 was occupied with the reading of "The Report to the Alloys 

 Research Committee," made by Prof. W. C. Roberts-Austen, 

 C.B., F.R.S. 



The first paper does not call for much attention at our hands. 

 It dealt exclusively with boiler-making practice, and can hardly 

 be of much interest outside the boiler-shop and draughting 

 office. Within these limits the paper is one of great value, 

 and therefore will occupy a most fitting place in the Proceed- 

 ings of the Institution. The contribution of Prof. Roberts- 

 Austen was of a very different description ; and although 

 it may not appeal so directly to the majority of mechanical 

 engineers, it can hardly fail to improve the practice of engine 

 construction, and advance the science of the production of 

 mechanical energy many steps nearer that ideal of efficiency 

 which is the goal all good engineers should keep in view. We 

 have on previous occasions dwelt upon the excellent work done 

 by the various Research Committees appointed by the Council of 

 this Institution, and we can think of no better way in which the 

 surplus funds of the Institution could be spent. Of all these 

 Research Committees, it may be said that that appointed to con- 

 sider the question of alloys is the most comprehensive and 

 important, for we appear to be fast coming to a period when 

 engines will consist almost wholly of two alloys — namely, brass 

 and steel. Cast-iron will naturally continue to be used for 

 massive parts where comparatively great weight is of small 

 importance, but wrought-iron is every day giving place to steel, 

 and steel castings have already almost entirely superseded those 

 of iron in positions where it is desirable to combine lightness 

 and strength. 



Prof. Roberts-Austen's report is a long document occupy- 

 ing twenty-four pages of the Proceedings, and illustrated by 

 several diagrams. We shall therefore, with the space at our 

 command, be able to do little more than give an outline of its 

 scope, or at any rate we can do no more than dwell on a few of 

 the more salient features. In dealing with the question of iron 

 and its alloys, the author assumed the reader to have an acquaint- 

 ance with the work of the talented French physicist Osmond, 

 of whom, as is well known, Roberts-Austen is a great admirer. 

 Osmond holds that the results of his experiments show that there 

 are two distinct varieties of pure iron — namely, the a or soft 

 form, and the ^ or hard form. M. Osmond, it will be re- 

 membered, set forth his views in a paper read at the meeting of 

 the Iron and Steel Institute, held in 1890.1 Mr. Roberts-Austen 

 had previously commenced an investigation upon the application 

 of the "periodic law" of Newlands and Mendeleeff to the 

 mechanical properties of metals, and the Research Committee 

 requested him to carry his work in this direction still further. 

 This law, as originally expressed, states that "the properties of 

 the elements are a periodic function of their atomic weights." 

 It has been shown that the effect of impurities added to gold is 

 nearly proportional to their atomic volume, the larger the 

 volume of the atom the greater being its effect.-' It became 



' See also Comptes rendiis, vol. ex., 1890, p. 346. 



^ Philosophical Transactions of the Royal Society, vol. clxxix., 1888, 

 P- 339- 



NO. I 149, VOL. 45] 



interesting to determine, therefore, whether this holds good for 

 other metals. Osmond had determined that the action of im- 

 puiities on iron does appear to be in accordance with the 

 periodic law ; and heliad arranged the elements in the following 

 order in accordance with their atomic volumes, found by divid- 

 ing their atomic weight by their specific gravity : — 



Carbon 3-6 

 Boron 4-1 



Nickel 67 



Manganese 6 '9 

 Copper 7 "I 



II. 



Chromium 77 



Tungsten 9*6 



Silicon 1 1 "2 



Arsenic 13 '2 



Phosphorus 13*5 



Sulphur 137 



Osmond pointed out that the elements in column I., whose 

 atomic volumes are smaller than that of iron (7'2), delay during 

 cooling, cceteris paribus , the change of hard iron into soft iron, 

 as well as that of "hardening carbon" into "carbide carbon." 

 For these two reasons they tend to increase, with equal rates of 

 cooling, the proportion of hard iron that is present in the 

 cooled iron or steel, and consequently the hardness of the metal. 

 The elements in column II. tend to raise, or maintain at 

 its normal position during cooling, the temperature at which 

 the change of hard to soft iron takes place. Further, they 

 render the inverse change during heating more or less in- 

 complete, and usually hasten the change of dissolved or 

 hardening carbon to carbide carbon. Thus they maintain iron 

 in the soft state at high temperatures, and must therefore 

 have the same effect in the cooled metal. In this way they 

 would act on iron as annealing does, rendering it soft and 

 malleable, did not their individual properties, or those of their 

 compounds, mask this natural consequence of their presence. 

 The essential part played by foreign elements alloyed with iron 

 is therefore either to hasten or to delay the passage of iron during 

 cooling to an allotropic state ; and to render the change more or 

 less incomplete in one direction or the other, according to 

 whether the atomic volume of the added impurity is greater or 

 less than that of iron. In other words, foreign elements of low 

 atomic volume tend to make iron itself assume or retain the 

 particular molecular form which possesses the lowest atomic 

 volume ; whilst elements with large atomic volume produce a 

 reverse effect. The report goes on to point out that the effect of 

 impurities on iron is far more complicated than in the case of 

 gold ; the latter being probably more simple in its molecular 

 structure. Also if iron, by itself, can exist in two widely 

 different states, the mechanical properties will be affected by 

 the proportion of each. Lead also, which was one of the metals 

 the Committee selected for investigation, probably exists in more 

 than one modification. The author had made many experiments 

 on the mechanical properties of lead as affected by a small 

 quantity of impurity, but had not brought the results to any con- 

 cordant or definite conclusion, and the inquiry was laid aside 

 for a time. The fundamental necessity in carrying out the work 

 of the Committee was a trustworthy pyrometer which would 

 measure higher temperatures, and fortunately an instrument 

 which appears to fulfil these conditions is now to be procured. 

 This, we need hardly say, is the Le Chatelier pyrometer. 

 This instrument consists of a thermo-couple of platinum 

 and platinum-rhodium wire, the record being obtained by 

 the measurement of the electric current produced. An auto- 

 graphic record is obtained by means of a spot of light 

 thrown from a mirror attached to the galvanometer which 

 measures the current. This spot of light is thrown on to a 

 sensitized plate (Eastman's film) which is caused to travel by 

 suitable means so as to give the time factor. The amplitude of 

 the deflection naturally gives the temperature of the substance 

 which is supplying the heat to the thermo-couple The calibra- 

 tion has been carefully effected by observations at known tem- 

 peratures ; and the instrument has been tested by observations 

 in connection with the liquation of silver-copper alloys, about 

 which a good deal is known. 



The report next proceeds to deal with the effect of small 

 quantities of impurity on the freezing point of gold — a metal 

 which offers special advantages for investigations of this nature, 

 as it may be prepared in a very high degree of purity, and is not 

 liable to contamination by oxidation. Moreover, much is 

 already known of its mechanical and thermal properties as in- 

 fluenced by small quantities of impurity. The effects of certain 

 alloys upon gold are given in the report, and are well worth 

 study on the part of those inquirers who wish to prepare them- 



